[Haskell-cafe] Re: problem with collection (container) class

Daniel Fischer wrote:

{-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE FunctionalDependencies #-} {- # LANGUAGE FlexibleInstances # -} module Leandro where

data Abb a b = Branch a b (Abb a b) (Abb a b) | Leaf

data ListAssoc a b = Node a b (ListAssoc a b) | Empty

class Container c a b |c -> a, c -> b where [...]

instance (Ord a) => Container (Abb a b) a b where [...]

Note: The FlexibleInstances Language pragma is required by GHC 6.8.1 and 6.8.2, but not by GHC 6.6.1 or hugs, I think that's a bug in 6.8.*

If it's a bug then it is probably in 6.6.1 too, it just gets hidden by the fact that in 6.6.1 the -fglasgow-exts extensions cannot be activated separately. If you enable one of them, you get them all. Cheers Ben